Method of treating ores



Patented Apr. 9, 1940 PATENT OFFICE METnon 0F TREATING DEBS Joseph T. Terry, South Pasadena, Calii'., assignor Angeles, Calif.

of one-half to Harland F. Beardslee, Les

0 No Drawing. Application June 18, 1938,

Serial No. 214,595

4 Claims.

This invention relates to ore-treating processes, and more particularly to the treatment of ores containing values difficult of recovery by any of the flotation concentration processes now conventionally employed. Not all valuable minerals are amenable to concentration by known methods of flotation. Generally only such as are called "sulphides respond to such treatment; whereas the other minerals, or such as may be called ox ides, because oxygen rather than sulphur is an important part of their composition, must be given a preliminary'treatment to make their recovery in a flotation concentrate practical'on a commercial basis. Lead minerals, especially, are apt to fall under one or the other of these classifications, as the sulphides of lead will float, whereas the oxides will not.

It is an object of the present invention, therefore, to provide a commercially feasible process of treating oxidized metalliferous, and particularly lead-bearing ores not susceptible to flotationconcentration in their natural state, such, for example, as lead sulphate (anglesite), lead carbonate (cerusite), and the like.

The invention possesses other objects and features of advantage, some of which with the foregoing will be set forth in the following description of, the preferred embodiments of my invention. It is to be understood that I do not limit myself to the embodiments here described, as I may adopt variations of the preferred embodiments within the scope of my invention as set forth in the claims.

The customary method of treatment of ore containing lead sulphate, lead carbonate, and similar values difllcuit to recover by flotation concentration in their natural state is to reduce the ore to a wet pulp, after which a soluble sulphide of sodium is introduced, for the purpose of forming a coating or fllm of sulphid on the oxidized metalliferous constituents of the ore, after which a concentrate is recovered by frothflotation.

I have found, however, that when the oxides are given a preliminary treatment with an alkali sulphide or alkaline-earth sulphid and alkali cyanide, they too become fiotable. has disclosed that sulphid filming of oxidized lead ores with soluble sulphids in water solution gives higher flotation recovery when alkali cyanide is present, because the alkali cyanide such as sodium cyanide or potassiiun cyanide, alters the exposed surface of the mineral particles suchas lead sulphate, carbonate and other lead minerals to cyanogen derivatives, at least in part.

The following assay results show the greater My research recovery of lead from orev pulp, when cyanide is used in conjuncition withsoluble sulphids:

Tailings from flotation test with sodium sulphid-assayed 1.85% lead.

Tailings from flotation test with sodium sulphid and sodium cyanide-assayed 0.6% lead. At pH value 8.5-50 milligrams sodium cyanide per litre of water was found effective.

The preferred manner of carrying out the process of the present invention, is first, to grind the ore in a ball mill in the presence of water, preferably rendered alkaline with sodium carbonate or calcium hydroxide, preferably to a fineness of sixty-five mesh, standard Tyler sieve, after which it is preferably modified with suitable reagents such as aerofloat 25", amyl xanthate, with or without other mineral collecting and frothing agent. The mixture is then subjected to a flotation operation, whereby a froth concentrate is recovered containing any gcld, silver, natural sul- 20 phids of lead, and the like which may be present in the ore. The ratio of ore to water is preferably 1 to 4 by weight. Calcium polysulphid and sodium carbonate are then introduced into the pref- .erably warmed pulp, to precipitate calcium and 25 therebyform sodium sulphid in accordance with the following chemical equation.

CaSz Na2C0s CaCO: NazS calcium sodium calcium sodium 30 polysulphid carbonate carbonate sulphid Sodium carbonate also defloculates the pulp; thereby aiding separation of the values from the gangue portion by froth flotation. Alkali cyanide is then introduced into the pulp in conjunction 5 with additional soluble sulphlds if required, and additional values recovered by a froth flotation operation.

I wish it to be understood that I do not limit myself to the definite amounts of the several rea-- 40 gents. The quantitative aspect of the present inof with water, treating said pulp with alkali cy- 55 anide and soluble sulphid to convert at least a part of the oxidized values to sulphids, and by froth flotation recovering a concentrate containing said sulphids.

2. The method of treating ore for the recovery of oxidized lead values,-which comprises sulphidizing said lead values by subjecting them to the action of sodium sulphid produced by the chemical reaction between sodium carbonate, sodium cyanide and calcium polysulphid, and then recovering a concentrate containing the sulphidizing lead minerals.

3. The method of treating ore for the recovery of oxidized metalliferous minerals which comprises reducing the ore to a pulp, introducing thereto a carbonate of sodium and a soluble sulphid of calcium to produce sodium sulphid in situ within the pulp whereby the metalliferous minerals of said ore are given a sulphid film, and recovering a concentrate from said pulp containing the sulphidized minerals, thereafter introducing alkali cyanide in the presence of a sulphidizing agent and a frothing agent, and by flotation recovering a concentrate containing sulphidfilmed oxidized minerals.

4. In a flotation process for the concentration and recoveryof oxidized ores of lead, the method of sulphidizing the lead constituents of the ore which comprises treating the pulp of said ore with calcium polysulphid and sodium cyanide to coat said lead constituents with a stable film of lead sulphid, thereafter precipitating the calcium with sodium carbonate to. deflocculate the gangue colloids, and subjecting the dispersed pulp to a froth flotation operation and recovering a concentrate containing lead.

V JOSEPH 'I'. TERRY. 

